• Structural Engineering and Mechanics
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• v.9 no.4
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• pp.383-396
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• 2000

A new structure-vibration-control approach is proposed which uses a passive coupling element between two parallel structures to reduce the seismic response of a system due to earthquake excitation. Dynamic characteristics of the two coupled single-degree-freedom systems subject to stationary white-noise excitation are examined by means of statistical energy analysis (SEA) techniques. Optimal parameters of the passive coupling element such as damping and stiffness under different circumstances are determined with an emphasis on the influence of the structural parameters of the system on the optimal parameters and control effectiveness. Numerical results including the root mean square values of the response due to the filtered white-noise excitation and the time-histories of response to El Centro 1940 NS excitation are presented.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.4
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• pp.152-159
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• 2005

The method of induction noise reduction can be classified by using passive control or active control method. However, the passive control method has a demerit to reduce the effect of noise reduction to low frequency (below) 500Hz) range and to be limited in a space of the engine room. Whereas, the active control method can overcome the demerit of passive control method. The algorithm of active control is mostly used in LMS (Least-Mean-Square) algorithm because it can obtain the complex transfer function easily in real-time. Especially, Filtered-X LMS (FXLMS) algorithm is applied to an ANC system. However, the convergence performance of LMS algorithm could not match if the FXLMS algorithm is applied to an active control of the induction noise under rapidly accelerated driving conditions. So, in order to solve the problem in this study, the Moving Bandpass Filter(MBPF) was proposed and implemented. The ANC using MBPF for the reduction of the induction noise shows that more noise reduction as 4dB than without MBPF.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.381-381
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• 2012

Noise control in underwater environments is an entirely different beast from its airborne counterpart, partly because of the orders-of-magnitude difference in density and compressibility between water and air. One of the most popular systems ever used for (passive) noise reduction under water is an anechoic coating known as "alberich," which was developed by the German during the Second World War and are still used today in naval applications. This talk looks back on some recent developments in underwater noise control, ranging from acoustic metamaterials to active noise control techniques, specifically geared to achieving underwater invisibility.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.134-137
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• 2014

The noise reduction performance of a passive facility is dependent on the its length or volume. In other words, this means that the larger the size of passive facility is, the better the noise reduction performance is. The sound directivity control has been proposed as an alternative for the noise reduction without a passive facility. The purpose of this study is to investigate the correlation between the flange attached to inclined exit of the tube and sound directivity when the sound radiates from the tube to the outside. As a result, the sound radiated from flanged tube had weak sound directivity in the wide angle. Also as the flange was bigger, the sound pressure level was lower in the behind the flange.

• Smart Structures and Systems
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• v.15 no.3
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• pp.831-846
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• 2015

Magneto-Rheological (MR) dampers are being used increasingly because of their adaptability to control algorithms and reliability of passive systems. In this paper, an extensive investigation on performance of MR dampers in semi-active and passive modes has been carried out. It is observed that the overall energy dissipation by MR dampers in passive-on modes is higher than that in semi-active modes for most of the competitive semi-active controllers. Based on the energy dissipation pattern, a novel semi-active controller, termed as "Simple Passive Semi-Active Controller", has been proposed for MR dampers. This controller can be emulated by a simple passive hardware proposed in this paper. The proposed concept of controller "hardware emulation" is innovative and can also be implemented for other semi-active devices for control algorithms of certain form. The effectiveness and reliability of the proposed controller has been investigated extensively through numerical simulations. It has been demonstrated that the proposed controller is competitive to or more effective than other widely used / investigated semi-active controllers.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.10
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• pp.1048-1054
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• 2004

The Passive acoustic control is used in various fields, such as structures, automobiles, aircraft and so on. It is used in variety of acoustic field with the absorbing material, as one of the methods which can control the acoustic in optional space. In that case of passive control using this absorption material, it would be important to maximize the control performance of material property, numbers, geometry shape and the attached location of boundary area of the absorbing material. But realistically these variables, specially material Property, have no broad choice. Therefore, the position of absorbing material is the most important variable. In this study, we use the optimization method to minimize acoustic energy of optional space in the interest frequency attaching some absorbing materials to the boundary area. For analysis and optimization, this study uses the FEA and the conjugate gradient method. This optimization process is very efficient and useful in the passive acoustic control.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.7
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• pp.1069-1076
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• 2012

We use largely two methods, how to control the noise of the KTX, they are the passive noise control method and the active noise control method. The passive noise control has been used in a variety of ways since the KTX opening day, but lately it has shown the technical limitations by being dropped sharply. So, it is getting important to conduct the research about ANC that is able to reduce the ambient noise when the environmental-factor changes and be installed easily. To reduce a three-dimensional closed-space sound field like a car of a high-speed rail is hard to do using single channel ANC control system. Therefore we have to model the paths of the noise exactly for reducing the noise. And the control speakers and the error mics should be designed for optimal position. In this paper, we designed the transfer functions for modeling the noise paths under the influence of the distance between control speakers & error mics and primary noise speaker in TEST-BED where there is modeled as actual interior of KTX. We have made the modeling and the simulations of interior environment of KTX car by using three frequency bands of 120Hz, 280Hz, 360Hz. After the modeling, we compared the performance of active noise control and also we analyzed what to affect with difference in distance. After comparing of the performance using Pure Tone 120Hz, 280Hz, 360Hz at each modeling and then we simulated ANC for KTX's interior noise which we measured really and analyzed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.310.1-310
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• 2002

Dynamic characteristics of smart laminated composite plates with passive constrained layer damping have been investigated to design structure with maximum possible damping capacity. The equations of motion are derived fur flexural vibrations of symmetrical, multi-layer laminated plates. The damping ratio and modal damping of the first bending and torsional modes are calculated by means of iterative complex eigensolution method. (omitted)

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.301-307
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• 1997

In this study, a new modified independent modal space control (IMSC), which relaxes the fundamental hardware limitation of IMSC, is suggested to handle vibration control problems using a virtual passive controller. This method has adapted a new stable switching algorithm between controlled modes and a virtual vibration absorber as a virtual passive controller in the independent modal space. It has been found that the new modified IMSC suggested in this paper, which can reduce the number of actuators, is shown to be simple and efficient in a realistic example of vibration control of a cantilever beam.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.2 no.2
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• pp.73-79
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• 2001

In this paper, the transmitted noise reduction performance of piezoelectric smart panels is experimentally studied. The proposed piezoelectric smart panels are comprised of plate structure on which piezoelectric sensor/actuators are bonded and sound absorbing material is provided. It is a combination of passive and active approaches utilizing a passive effect at high frequencies and an active effect at low frequencies. To prove the concept of piezoelectric smart panels, an acoustic measurement experiment is performed. An acoustic tunnel is designed and its acoustic characteristics are tested. Below 800Hz, the tunnel exhibits a plane wave guide characteristics. When an absorbing material is bonded on a single plate, a remarkable transmitted noise reduction in mid frequency range is observed except the first resonance frequency. By enabling the active control of single smart panel with negative feedback control. about 10dB noise reduction is achieved at the resonance frequencies. The double smart panel got 4dB at the first resonance frequency and has more potential to reduce the transmitted noise in a wide range frequency. Piezoelectric smart panels incorporating passive absorbing material and active piezoelectric devices is a promising technology for noise reduction in a wide range frequency.